Compounded mineral oil



Patented Nov. 21, 1944 UNITED STATES PATENT OFFICE 'Robert J. Miller and John '1.

Rutherford,

No Drawing. Application May 6. 1942,

Serial No. 441,964

19 Claims.

This invention relates broadly to improvements in viscous mineral oils, greases and the like, and more particularly to mineral lubricating oils which are stabilized against oxidation and rendered less corrosive to bearing-type alloys and which possess superior engine performance characteristics.

The more viscous mineral oils, used as lubricants, transformer oils and the like and in greases, vary widely in chemical composition both with respect to the main or hydrocarbon components, such as the parafllns and naphthenes, and with respect to the minor or nonhydrocarbon components, such as naturally contained naphthenic acids and sulfur compounds. Moreover, processes employed in refining such oils vary the amount and nature ofthe hydrocarbon and non-hydrocarbon components of the oil.

It is recognized that the chemical composition of viscous mineral oils is reflected in their properties as lubricants and the like: for example, their tendency to oxidize in the presence of oxygen and form sludge; their tendency to corrode certain bearing-type alloys, such as copper-lead and cadmium-silver alloys; and their tendency to cause discoloration of pistons and sticking of'piston rings. Film strength, oiliness and pour point are also influenced by chemical composition. m

A great amount of attention has been given to control of the chemical composition of viscous mineral oils in order to control the properties affecting their utility as lubricants, dielectric media and the like. Besides control from the refining end, which appertains more to the removal of undesirable constituents from the oil by Physical or chemical means or their conversion by heat and/or chemical reagents into more desirable products remaining inthe oil, much work has been done on the incorporation in oils of chemical agents to control their properties.

In this largely empirical science of compounded oils, that is, the science of incorporating chemical substances in oils and the like there has developed the knowledge that a conhesive deposits on cylinder walls and in piston ring slots. Oxidized oils also tend more readily to emulsify and are, therefore, less fit for use in siderable number of distinct but interrelated properties control the final quality of the oil. Thus mineral lubricating oils all have a tendency to oxidize in the presence of air or combustion products of hydrocarbons, especially at a.

high temperatures and under high pressures. Among the disadvantages of such oxidation is the formation of sludge in the oil and of solidadcontact with water; therefore less fit for for use as turbine lubricants. Moreover, certain oils are either initially corrosive to the aforesaid bearing-typ'e alloys or they become corrosive after service. Some lubricating oils tend more than others to form deposits of carbon on pistons and to cause sticking of piston rings.

In the control of these and other properties it has been proposed at various times by various workers to add to viscous mineral oils one or more additives. The total number of such proposed additives is enormous and even the broad classes of organic and organo-lnorganic compounds heretofore proposed as compounding agents are numerous and cover a large portion of the field of organic and organo-inorganic compounds. It may be said that there are listed in the prior art numerous compounding agents for the improvement of lubricants with respect to any oftheir recognized properties, such as resistance to oxidation, corrosivlty, piston dis coloration and piston ring sticking.

However, many of the proposed compounding agents effect improvement with regard to oneproperty without improving other properties and many of the compounding agents efiect improvement of-an oil with respect to one or more selected properties but actually have a harmful effect on other properties. This is not to say that such agents of limited utility or of mixed good and bad qualities are not useful. Many of them are highly useful and some are valuable components of the highest quality mineral oil products. However, in many cases a combinahave the drawback that they cause corrosion of bearing-type alloys. Accordingly, their utility in types of service where they are brought into contact with susceptible alloy bearings is somewhat limited. In such types of service it is necessary ,to combine with the metal salt detergent a corrosion inhibitor. Illustrative or metal salt detergents which promote corrosion or bearing-type alloy a are the metal naphthenates,

metal soaps of fatty acids, metal phenates and metal alcoholates.

Further important factors affecting the utility of a mineral oil compounding agent are its solubility in oil, its stability at high temperatures and pressures, its stability toward oxidation and its cheapness.

It is an object achieved tion to improve various properties of viscous mineral oils. 7

It is a further object achieved by the present invention to efiect improvement of viscous mineral' oils by the use of certain compounding agents without producing undesired efiects.

It is a still further and particular object achieved by the present inventionto stabilize petroleum lubricating oils against oxidation, to inhibit their corrosiveness toward bearing-type alloys, and to bring about an improved performance of the oil with respect to piston discoloration, piston ring slot clogging, piston ring sticking and the like, all by the use of a single class of compounding agents.

Other objects achieved by the invention will be apparent from the description and the claims.

We have discovered that certain novel petroleum nitrogen base derivatives and other like nitrogen base derivatives have very superior properties as compounding agents for viscous mineral oil compositions, especially petroleum lubricating oils. 4

Illustrative of the nitrogen base derivative used in accordance with theinvention are the prod uctsobtained by extracting the cyclic nitrogen base derivatives present in certain petroleum oils,

which are largely a. mixture of alkyl substituted by the present invenpyridines, reducing'the extracted mixture to the corresponding alkyl substituted piperidinesfand reacting the reduced mixture with an equivalent amount of carbon disulfide in the presence of an aqueous caustic alkali' solution. There is thus produced an alkali metal dithiocarbamate, which may be recovered by crystallization, but other metal dithiocarha ates, such as polyvalent metal dithiocarbamatesY nay be produced by adding a soluble salt of the polyvalent metal to the aqueous solution of alkali metal salt, thereby precipitating the insoluble polyvalent metal salt. Salts thus, produced we have found to be excellent additives or compounding agents for lubricating oils and the like.

- Petroleum nitrogen bases have heretofore been proposed as compounding agents for lubricating oils,'for example in Ihrig United States Patent No. 1,768,910, but better results are obtained by reducing the bases and converting the reduced bases into dithiocarbamates in accordance with this invention.

The compounding agents of our invention, even when used in small amount, effect several marked improvements in viscous mineral oils, greases, and the like, especially mineral lubricating oils. Thus they increase very substantially the resistance of mineral oil to oxidation and they inhibit corrosion of alloy bearings by mineral oils and/or other additives contained in the oil. They also result in improved engine performance of the oil; that is, they decreasethe amount of ring sticking, piston discoloration and oil ring slot clogging.

Moreover, the compounding agents of our invention are soluble in a wide variety of oils, such as paraflin base, naphthene base and mixed base oils, and they are stable toward heat and oxygen. They are also easily prepared from readily availabl materials.

EXAMPLE 1 PREPARATION or NITROGEN Bass Dmzrvnrrvss A' crude cracked -n'aphtha, as obtained in the pyrogenetic cracking of a nitrogen-containing crude petroleum oil or-distillate, is extracted at ordinary temperatures with dilute aqueous sul-' furic acid, of a concentration generally about 50% H2804, and water-soluble sulfates of mixed petroleum nitrogen bases are thereby formed. The petroleum nitrogen bases are recovered by neutralization with a dilute aqueous alkali metal hyroxide solution, and they are sufliciently waterinsoluble to permit of stratification and decantation. In a typical case, a mixture of the crude bases thus separated from a crude cracked 100- 500 F. naphtha of California petroleum origin had a specific gravity of 0.9370, a basic dissociation constant of 4X 10-, an average molecular 'weight of about 146, and an A. S. T. M. distillation boiling range between 340 and 444 F. (5% point, 394; 90% point, 418 F.). After such recovery, the petroleum nitrogen bases are reduced to secondary amines, and such reduction may be accomplished by metallic sodium in alcoholic solution, electrolytically in dilute acidsolution, or by hydrogenation under pressure in the presence of a suitable catalyst. In the latter method of reduction, MoS: deposited on charcoal may be the catalyst, and mol ratios of hydrogen to nitrogen base between l0 to. 1 and 50 to 1 may be employed, at pressures of about 200 atmospheres; CS2 or an analogous sulfur carrier should be introduced, as (NH4)2S is formed during the reduction and desulfurization of the catalyst may prejudice the recovery of high yields of the reduced bases. The temperature of hydrogenation should be between 475 and 650 F.; 575 F. is a good average, and the temperature should not exceed 700 F. A suitable space rate is 0.3 volume of liquid charged/hour/volume of catalyst. In a typical reduction of nitrogen bases by such a hydrogenation, 56% of the bases were reduced to secondary amines, 7% were decomposed and 37% were unreduced or unreacted upon. After reduction, whether electrolytically, by metallic sodium or by hydrogenation, the secondary amines are recovered from the reaction product mixture by adjustment of pH to approximately 8.5. in aqueous solution; unreduced nitrogen bases remain water-insoluble, while the reduced bases by reason of their higher basicity pass into water solution as salts. Excess alkali metal hydroxide is then added to liberate the reduced bases, which are sufficiently water-insoluble to permit of stratification and decantation. .In. the above typical case, a mixture of th petroleum nitrogen bases thus reduced (in their free form) had a specific gravity of 0.848, a basic dissociation constant of 1 10 an average molecular weight of 157, and

' an A. S. T. M. distillation boiling range between aeoaoia soluble tothe extentof 2.5% by weight in water at 60 F.

Subsequent to the reduction of the cracked petroleum nitrogen bases to secondary the corresponding alkali metal dithiocarbamic acid salts maybe prepared by reacting CSa and aqueous alkali metal hydroxide, for example potassium hydroxide, with the nitrogen base secondary amines, in stoichlometric proportions and at atmospheric temperature, in suillcient water to produce a 50% solution of the product: the reaction proceeds in almost quantitative yield and the desired reaction products are freely watersolubie. In the above typical case. in a sequence of steps such as that outlined. there was ultimate- 1y obtained a 50%aqueous solution of a mixture of potassium reduced cracked petroleum nitrogen base dithiocarbamates appearing as an amber liquid, specific gravity 1.11' (60*"12/60' it), with nitrogen and sulfur contents of 2.56 and 11.7% respectively. 1

Theheavier metal derivatives oi these substances may be prepared by the addition of an aqueous solution of a water-soluble salt of the desired metal to an aqueous solution of an alkali ,metal salt of the dithiocarbamic acid derivative.

For example, a'dilute aqueous zinc chloride soluti'on, added to an aqueous solution of the sodium or potassium reduced cracked petroleum nitrogen base dithiocarbamates, prepared in accordance with the methods referred to, causes the precipitation of the water-insoluble zinc salt. and this is collected, washed thoroughly with p p p 3 dissolved in ms. A. a. an naphthene base oil,

also in an S. A. E. Pennsylvania (parafllnic) oil, in amounts ranging from 0.1 to 1.0 percent. Samples of grams each of base oil and compounded oil were taken and oxygen was bubbled through each sample, the temperature or the oil being maintained at 340 F. and all other conditions, such as oxygen pressure and rate and duration of bubbling, being maintained the same for-each sample. Part of the oxygen was absorbed bythe oil. the amount absorbed being.

determined by calculating the difference between unabsorbed oxygen and the oxygen fed to the sample of oil. The results are set forth in Tables I and 11 below. The various metal salts in the tables refer to the above-described metal dithiocarhamates.

Table 1 Cubic centimeters of oxygen absorbed aiter Oil 0.5 1.0 1.5 1.9 2.0 7..5' 3.7 hour hour hours hours hours hours hours 8. A. E. 3Unaphthenc base oil 56 146 226 286 325 Same+0.5% 0! K salt. 16' 30 58 96 128 Same-{4.0% of Ca calf 230 Samo+0.5% of Zn 30 70 130 Same+l.0% of Zn 42 72 96 144 Sexual-1.0% 0! Sn salt 78 234 Table II Cubic centimeters of oxygen absorbed after-- Oil hour hour hour hours hours hours hours hours S. A. E. 30 Pennsylvania (paraflinic) oil 68 178 254 '302 Same--0.5% of Zn salt- 38 45 57 69 Same-415% of Zn salt-{415% metal alkyl phenate- 66 90 Same- 0.25% of Zn salt-l-0.5% metal alkyl BL '80 94 112 2.74 Same- 0.1% of Zn salt+0.5% metal alkyl phena 82 water, and dried. Other heavier metal deriva- EXAMPLE 3 tives suitable in the practice of our invention,

for example, the lead salt, may be similarly prepared.

From the properties and reactions of the di- -thiocarbamates as well as those of the cracked petroleum nitrogen bases from which they are derived, it is deduced that the dithiocarbamates of this invention are predominantly one or more,

probably a mixture of the substances having the following structural formulae:

, In the above formulae, R1, R2 and R3 represent alkyl groups, which may be attached at the points shown or at other points on the piperidine ring, and R1 and the sum Ra-l-Rs each contains an average of 5 carbon atoms.

EXAMPLE 2 Oxmarron Tss'rs Potassium, calcium, zinc and tin '(stannous) salts, prepared as described in'Example 1, were CORROSION am) Enema Tas'r's The above-described zinc dithiocarbamate was incorporated in various oils and submitted to tests to determine its efiect on corrosion of bearing-type alloys and its effect on ring sticking.

piston discoloration and oil ring slot clogging.

The tests were carried out as follows:

Bearing metal corrosion test.This test is described in United States Patent No. 2,228,658 to Farrington et al. at page 3, right-hand. column, lines 27 to 65. Briefly, the test comprises bub bling air through an oil maintained at 300 F.

and at 24 hour intervals weighing strips of copper-lead and cadmium-silver bearing-type alloys which are kept immersed in the oil, to determine the loss in weight of the strips. This loss in weight is a. measure of the amount of corrosion, being greater the greater the corrosion.

Ring sticking, piston discoloration and oil ring slot clogging test (engine test) .-A single cylinder 2% inch bore, 2 /2 inch stroke Lauson gasopistons and sticking of the piston'rlngs. At the end of each 60 hour run the engine is disassembled and the'results noted. The piston appearance is rated as follows: A completely clean piston rates zero and a piston with completely black sides rates 800. Piston discoloration numbers (P. D. numbers) between zero and 800 indicate approximately, on a scale of 800, the proportion of blackening.

bamate type; that is, in which the ring nitrogen of the piperidine residue is also the nitrogen of the characteristic dithiocarbamate group may be used whatever the source of the piperidine or piperidine homologue. Also, other rings may In Tables III and IV are given the results of replace the piperidine ring; for example, four, the bearing metal corrosion tests and the engine five and seven member rings. Typical examtests for the various oils. ples of nitrogen base derivatives coming within Table III Weight loss of strip in milligrams Base hi1 Additives Cu-Pb alloy Gd-Ag alloy 24hrs. 48hrs. 72 hrs. 24hrs. 48h1's. 72 hrs.

None 0.2 0.7 1.1 +0.1 +0.2 +0.4 0 0.5% Zn dithiocarbamate. 0. 4 +0. 9 +1. 5 +0.3 +0.7 +1. 1 0.5% metal alkyl phenate 4. 5 l9. 5 27. 4 0 0 0 D 0.5% metal alkylphenate+0.25% Zn dithiocarbamate. 1. 2 5. 3 24. 4 0 0 0 D 0.5% metal alkyl phenate+0.5% Zn dithiocarbamate. 0. 8 1. 0 1. 9 0. 1 0. 1 0. 3 None 1.6 4.5 11.2 0.1 0.1 0.1

n 0.5% Zn dithiocarbamate. 0.9 1.3 1.9 0.1 0.2 0.4

Do 0.75% metalalkylphenate 18.5 107.3 150.0 5.9 111.9 215.4

-Do 0.5%metalalkylphenate+0.25%Zndithiocarbamate. 1.0 17.2 51.9 0.1 8.5 31.9

Do 0.5% metal alkyl phenate+0.5% Zn dithiocarbamate. 0. 7 2. 6 16. 2 0. 1 0. 2 0. 3

. one 0.2 0.0- +0.0 +0.2 +0.2 +0.0

n 1%Zndithiocarbamate..--

Do 0.5% metal alkyl phenate 17.0 44.0 81. 5 3. 7 36. 5 60. 7

Do 0.5%metal alkylphenate+0.5% Zn dithiocarbamate. 0.7 7.6 34.7 0.1 0.4 0.1

Table IV Ou-Pb bear- N f Percent Base oil Additives rl ig ring slot f g fi stuck clogging milligrams 0i1No.1 None Two 600 80 16 Do. 0.5 Zn dithiocarbamate None 250 70 8 Oil No. 2 0.5 Zn dithiocarbamate+ do- 255 0 3 0.5% metal alkyl phenate.

In Table III, a plus sign in front of anumthe broader aspects of the invention are the folber indicates that the alloy strip increased rather lowing: than decreased in weight. In Tables III and IV S the base oils designated as Oil No. 1,.Oil No, 2, v g I! etc. were the following types of oil:

CH 011 No. 1Naphthene base. 2 Oil NO. 2California parafiin base. Four membered ring Oil No. 3Pe nnsylvania paraflln base. CH CH S Oil No.-4Gulf Coast naphthene-paraflin base. 2-

. N-C-S-M With reference to Table III, a loss in weight of l either alloy strip of 15 milligrams in 72 hours 5 represents about the borderline between a nonr Five membered ring corrosive and a corroslve 011. Oils which sustained more than 15 milligrams loss of weight in CHI-CH7 i 72 hours under the conditions of the bearing on, NC-S-M metal corrosion test are classifiable as "corrosive CH CH oils, whereas oils which sustained less loss of 2 weight are classifiable as non-corrosive oils. Six member ed ring Further with respect to Table III, it will be noted OH H H that the zinc dithiocarbamate in no case ren- To s dered corrosive a normally non-corrosive oil, and O- M in those cases where an oil was corrosive, the (.H,0H-0H, zinc dithiocarbamate greatly decreased the corrosiveness of the oil or rendered the oil non-cor- Seven membeedrmg rosive. In these formulae the nitrogen rings may be sub- Besides the petroleum nitrogen base derivastituted, as by alkyl groups, and M stands for tives hereinabove described, other similar nitrothe hydrogen equivalent of a metal; that is, so gen base derivatives, whether of petroleum orimuch of a metal as is not satisfied by other gin ornot, and whether the nitrogen base is of groups. Part or all of the valencies of a polynatural or synthetic origin, may be advantageousvalent metal may be satisfied by the nitrogen 1y used in lubricating oils, and such use is within ring dithiocarbamate radical.

. the purview of the invention. Broadly speaking, therefore, the present inven- Thus piperidine derivatives of the dithiocartion comprises the use in oils and the like of nifollowing formula:

trogen ring dithiocarbamates represented by the S x-rLs-m X is a nitrogen-containing ring attached to the Quite small amounts, on the order of 0.05 to 4 per cent by weight based on the finished prodgroup through the ring nitrogen, and C and Sv have their usual significance.

Preferably, however, we use those nitrogen ring dithiocarbamates in which, as in the herein described reduced petroleum nitrogen base dithiocarbamates, the nitrogen ring bears one or more alkyl substituents, and preferably those that contain at least 5 carbon atoms in the alkyl group or groups attached to the nitrogen ring. The most advantageous oil compounding agents of all the the petroleum nitrogen base dithiocarbamates described hereinabove in detail.

Various metals may take the place of M in the above type formula; for example, sodium, potassium, copper, magnesium, calcium, strontium, barium, zinc, aluminum, tin, lead, chromium, molybdenum, manganese, iron, cobalt and nickel, although zinc and calcium are preferred.

Some oils, such as certain excessively treated oils, are normally corrosive to certain bearing alloys. Other oils are normally non-corrosive toward such alloys but are 'renderedcorrosive thereto by the addition of various compounding agents, such as theaforementioned metal salts of organic acids or acid-acting substances, comprising certain metal naphthenates, metal soaps of fatty acids, metal phenates and metal alcoholates. Specifically, the following metal salts of organic acids, phenols and alcohols, among others, cause oils to be corrosive or more corrosive toward bearing-type alloys: aluminum naphthenate, calcium naphthenate, magnesium naphthenate, aluminum stearate, calcium stearate, calcium phenylstearate, calcium dichlorostearate, calcium benzolstearate, aluminum oleate, calcium oleate, barium cetylphenate', calcium cetylphenate, potassium cetylphenate, calcium octadecenolate, sodium octadecenolate. Many of these compounding agents are useful in lubricating oil, for

. of caustic alkali solution, and precipitating the zinc salt by adding a soluble zinc salt to the alkali solution, as described in Example 1. The preferred combination of agents according to our invention are mixtures of our metal dithiocarbamates and metal alkyl phenates, in particular the said zinc dithiocarbamate and alkaline earth metal alkyl phenates such as calcium cetyl phenate and other alkaline earth metal phenates containing higher alkyl substituents. These mixtures combine in high degree the valuable properties of each component with fewer if anyof the disadvantages of the components taken separately.

not, of the dithiocarbamates of the invention are in most cases sufllcient to bring about the desired effect in viscous mineral oil compositions,

although in special cases greater amounts may 7 be advisable. Greater amounts, for example from 5 to 50 per cent by weight on the oil, may also be incorporated in mineral oil to produce: a; con- 1 centrate, which, pan be more conveniently stored and transported and, when required, mixed with more oil to produce lubricant containing the proper proportion of compounding agent. The

dithiocarbamate may be combined with another l additive, such as one of the aforementioned metal salt detergents, in such a concentrate.

The compounding agents of our invention are useful generally in combination with mineral oils, as in crankcase oils, gear lubricants, transformer and switch oils, greases, etc.

The dithiocarbamates disclosed hereina'bove are claimed as components of greases in our copending' application Serial No. 521,438, filed February 7, 1944.

We claim:

1. A composition of matter comprising a viscous mineral oil and a small amount, suihcient to stabilize the oil against oxidation of a. nitrogen base derivative in whichthe nitrogen forms Part of a ring and is attached to the group wherein M is the hydrogen equivalent of a polyvalent metal.

2. The composition of claim 1, wherein the '7 metal M is an alkaline earth metal.

3. The composition of claim 1, wherein the metal M is zinc.

4. A compound lubricating oil, comprising a major amount of viscous petroleum oil and a minor amount, suificient to improve substantially the lubricating characteristics of the oil, of 9. ni-

trogen based derivative in which the nitrogen forms part of an alkyl substituted ring, the total number of carbon atoms in the alkyl substituent or ,substituents being at least 5, and in which the nitrogen is attached to the group cient to improve substantially the lubricating characteristics of the petroleum oil, of a polyvalent metal dithiocarbamate of which the dithiocarbamate nitrogen atom forms part of aring derived from nitrogen-containing cracked naphtha by extraction of pyridine bases from the naphtha, reduction of the extracted pyridine bases, and reaction of the reduced pyridine bwes with carbon disulfide.

9. The compounded oil of claim 8, wherein the petroleum lubricating oil is anaphthenic oil.

10. The compounded oil of claim 8, wherein the petroleum lubricating oil is a paramiiic oil.

11. The compounded oil of claim 8, wherein v the metal salt is an alkaline earth metal salt.

12. The compounded oil of claim 8, wherein the metal saltis a calcium salt.

13. The compounded oil of claim 8, wherein the metal salt is a zinc salt. v

14. A compounded lubricating 011, comprising a major amount of petroleum oil oi. lubricating vissubstituents being at least 5, and in which the nitrogen is attached to the group H CSM wherein M is the hydrogen equivalent oi a polyvalent metal. .1 v

' 15. The oil of claim 14, wherein the corrosive metal salt is a metal naphthenate. v

16. The oil of claim 14, wherein the corrosive metal salt is a metal soap ot'a fatty acid.

17. A composition of matter, comprising a concentrated solution in viscous mineral oil of a nitrogen base derivative in which the nitrogen forms part of a ring and is attached to the group wherein M is the hydrogen equivalent of a polyvalent metal.

18. A compounded lubricating oil comprising a petroleum lubricating oil and about 0.1 to 4 per cent by weight based on finished on of a polyvalent metal dithiocarbamate in which the dithiocarbamate nitrogen forms part of an alkylated piperidine ring.

19. The oil of claim 18, wherein said polyvalent metal salt is a zinc salt.

ROBERT J. NIILLER. JOHN T. RUTHERFORD. 

